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所谓质量不变法,就是在解溶液计算题时,根据溶液在变化前后,溶质(或溶剂)的总质量保持不变,列式计算。 例1 将浓度为20％的NaNO_3溶液50克,倒入140克100℃的NaNO_3饱和溶液里,然后降温到20℃,有21.7克NaNO_3析出。求20℃时NaNO_3的溶解度。(NaNO_3的溶解度:100℃时为180克) 解法 1:设20℃时NaNO_3的溶解度为s克。 50克溶液里NaNO_3是50×20％克,140克溶液里NaNO_3是140×(180)/(100+180)克,结晶后的20℃饱和溶液
The so-called mass invariance method is that when the solution solution is solved, the total mass of the solute (or solvent) remains unchanged before and after the change of the solution. Example 1 50 g of a 20% strength NaNO 3 solution was poured into 140 g of a saturated NaNO 3 solution at 100°C, and then cooled to 20°C, and 21.7 g of NaNO 3 precipitated. Solubility of NaNO 3 at 20°C. (Solubility of NaNO_3: 180 g at 100°C) Solution 1: The solubility of NaNO_3 at 20°C is sg. In a 50-gram solution, NaNO 3 is 50×20% grams. In 140-gram solution, NaNO 3 is 140×(180)/(100+180) grams. After crystallization, a saturated solution at 20°C is used.